1. Field of the Invention
The present invention relates to a seat cushion frame for use in a vehicle seat, and particularly to a die-cast seat cushion frame having a reinforced structure.
2. Description of Prior Art
A vehicle seat has a seat frame as a main supportive skeleton. Recently, the seat frame has been made light in weight by being formed from a light alloy such as aluminum alloy or magnesium alloy.
Typically, as disclosed from the U.S. Pat. No. 5,897,168 for instance, a seat frame is formed by die casting, using a magnesium alloy, into a predetermined quadrangular seat frame configuration, which therefore makes forming seat frame easy and rapid.
This sort of die-cast frame is, however, reduced in rigidity and robust in comparison with a steel frame assembly formed by firmly fastening several steel plate pieces to one another. To compensate for this disadvantage, it has been a common practice to attach a steel reinforcing plate to the vulnerable points of die-cast frame which are susceptible to a great load and prone to deformation thereby. Particularly, in the case where a pair of steel slide rails are fixedly connected with the respective two lateral frame sections of a die-cast seat cushion frame, there are normally defined forward and rearward connecting points in each of the two lateral frame sections for firm connection with the respective two slide rails. Then, those two connecting points naturally require additional reinforcements in view of the afore-said less robustness of die-cast frame. For that purpose, conventionally, a reinforcement plate has been attached to each of the connecting points of die-cast seat cushion frame together with the slide rails, sufficient to withstand an intensive exertion of great load thereon. Or, in alternative conventional way, each of those connecting points has been formed to increase its thickness to a considerable degree during die casting process so as to give a sufficient strength thereto.
But, in both such reinforcing effects, the weight of die-cast frame itself becomes increased to impair the lightweight purpose and costs of material also increase due to a greater amount of aluminum or magnesium alloy used. Further, there has been no particular design in the seat cushion frame to receive a seat occupant""s buttocks portion in the case of a sudden deceleration or collisions case so as to prevent the occupant""s buttocks portion from being moved downwards below the seat cushion frame via a cushiony upholstery layer on the frame and slid forwards on the surface of upholstery, passing through a seat belt on his or her body into an undesired state.
In view of the above-stated drawbacks, it is a purpose of the present invention to provide an improved die-cast seat cushion frame for vehicle seat which is of a light yet robust construction and serves to prevent forward slippage of a seat occupant""s buttocks portion relative to the seat cushion frame.
To achieve such purpose, a die-cast seat cushion frame for seat cushion of vehicle seat in accordance with the present invention is basically comprised of:
a forward frame portion defined forwardly thereof;
a rearward frame portion defined rearwardly thereof;
a pair of lateral frame portion defined between the forward and rearward frame portions;
at least two connecting portions integrally formed in each of those two lateral frame sections; which at least two connecting portions are adapted for connection with a slide rail means; and
a cross beam portion extended integrally between the two lateral frame sections in such a manner that one end of the cross beam section is disposed at a point corresponding to one of the at least two connecting portions while another end of the cross beam section is disposed at a point corresponding to another of the at least two connecting potions.
Accordingly, such simple provision of the cross beam portion does not require any separate reinforcing elements and neither do it require unnecessary increase of thickened portions in the seat cushion frame, either. This is much effective to the die-cast seat cushion formed from such light alloy as magnesium or aluminum alloy. Further, since the cross beam portion is disposed transversely of the seat cushion frame, a buttocks portion of an occupant on a seat cushion (i.e. the seat cushion frame) will be positively received by that cross beam portion when the buttock portion is sunk greatly below the seat cushion frame in a sudden deceleration and collision case, thereby protecting the occupant from the above-stated forward slippage problem.
Preferably, the cross beam portion is of generally inverted-U-shaped configuration in cross-section and both ends thereof are integrally connected via gusset portions with the respective inner walls of the two lateral frame portions.
It is another purpose of the present invention to reinforce the two lateral frame portions without increase of their respective thicknesses. For that purpose, a generally U-shaped beam portion is defined in and along the inner wall of each of the two lateral frame portion. Additionally, an upper flange portion is formed in the upper end of each lateral frame portion, projecting outwardly therefrom, and a lower flange portion is formed in the lower end of each lateral frame portion, projecting inwardly therefrom.
It is still another purpose of the invention to make more rigid the foregoing connecting portions to efficiently disperse a load applied thereto and escape therethrough to the slide rail means. For that purpose, the connecting portions are large in thickness relative to the lateral frame portions and so formed that the outer walls thereof are coplanar with the outer vertical surfaces of the lateral frame portions.
Other various features and advantages of the present invention will become apparent from reading of the descriptions hereinafter with reference to the annexed drawings.